The paper deals with transients attendant on filter-compensating capacitive units (FCU) switching-off. The transients disturbs the converter operating mode, breaks the valves commutation, which may caused a converter turn-off. Such processes are caused the saturation of the voltage transformers, used for control of the converter, at FCU switching-off. The problem can be solved by the use of voltage transformer with insulated neutral or ungrounded FCU. These means allow avoiding dangerous current values of primary windings of voltage transformers. To verify the efficiency of proposed means, the digital simulation and natural experiments on back-to-back link between the Russian and Finnish grids were carried out.